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Degradation profile and dioxygenase activity of <i>Carnobacterium gallinarum</i> (mt350233) and <i>Enterococcus faecalis</i> (mt345788) isolated from landfill soil in Benin City


F.I. Okolafor
J.O. Osarumwense
F.O. Ekhaise

Abstract

Landfill is a potential microbial hub of hydrocarbon (HC) degrading bacterial population owing to nutrient availability and continuous enrichment by organic materials. The degradation and dioxygenase activity of Carnobacterium gallinarum and Enterococcus faecalis isolated from landfill soil in Benin City was investigated. Soil samples were collected from a Government approved landfill in Benin City at a depth of 0 to 10 cm. Standard microbiological and molecular methods were followed for the isolation and characterization of bacterial population. Bacterial isolates were standardized for degradation using spectrophotometer optical density (OD) 0.08 at 600 nm (equivalent to 1×108cfu/ml). The gas chromatography with flame ionization detector (GC-FID) method was used to determine the total petroleum hydrocarbon (TPH) of waste engine oil (WEO) containing samples. The spectrophotometric methods were used for the assay of catechol 1,2-dioxygenase (C12O) and catechol 2,3-dioxygenase (C23O) activity. The result of the 16S rRNA analyses of the bacterial isolates confirmed the identity of Carnobacterium gallinarum as 98.71 % and Enterococcus faecalis as 100 %. The degradation profile of Carnobacterium gallinarum and Enterococcus faecalis at varied concentrations (20, 40, 60, 80 and 100 mg/L) of WEO showed significant decline in optical density (OD) values from day 1 to day 7. The decline in OD is an indication of utilization of Polycyclic Aromatic Hydrocarbons (PAHs) present in the WEO. The result of the gas Chromatography with Flame Ionization Detector (GC-FID analyses) of degraded WEO containing samples revealed the absence of low molecular weight and high molecular weight PAHs after the 7-days degradation study. The presence of HC degrading enzyme in the bacterial isolates was confirmed by the production of C12O and C23O as a result of the formation of cis, cis muconic acid and 2-hydroxymuconic semi-aldehyde respectively. This study revealed that the landfill soil is a potential natural microcosm for WEO degrading bacteria and possesses biologically active HC degrading bacteria population such as Carnobacterium gallinarum and Enterococcus faecalis.


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eISSN: 1118-1931
print ISSN: 1118-1931